Frequency and properties of low-level jets from two years of sodar data Stefan Emeis [email protected] INSTITUTE OF METEOROLOGY AND CLIMATE RESEARCH, Atmospheric Environmental Research KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association www.kit.edu Low-level jets results from SODAR observations 2 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research Monthly mean vertical wind profile August 2002, 17 nights with LLJ 3 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research Monthly mean diurnal course of wind speed wind speed in m/s August 2002, 17 nights with LLJ local time 4 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research examples for low-level jet observations with SODAR vertical profiles of wind speed 26 June 2005 AdP Ch d G 5 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research examples for low-level jet observations with SODAR vertical profiles of wind direction 26 June 2005 AdP Ch d G 6 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research examples for low-level jet observations with SODAR vertical profiles of wind speed (30 min means) 23-30 June 2005 AdP Ch d G 7 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research Mean diurnal variation of the turning of wind direction with height Emeis, S., 2001: Vertical variation of frequency distributions of wind speed in and above the surface layer observed by sodar. Meteorol. Z., 10, 141-149. 8 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research Nocturnal low-level jet and the turning of wind direction with height Day T well-mixed boundary layer Night stable BL 29.01.2014 H R T P 9 C P Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations C H Institute for Meteorology and Climate Research – Atmospheric Environmental Research surface pressure 00 GMT 26 June 2005 asterisk denotes location where LLJ was observed 10 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research One of the first larger SODAR campaign 5 2001 6 2001 7 2001 8 2001 9 2001 10 2001 11 2001 12 2001 1 2002 2 2002 3 2002 4 2002 5 2002 1 2003 2 2003 3 2003 4 2003 8 2002 9 2002 10 2002 11 2002 12 2002 METEK DSDR3x7-SODAR of IMK-IFU in Hannover-Linden Two years of measurements at one and the same site 11 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research frequency of LLJ over Hanover for 20 months in the years 2001 to 2003 total is 22 % of all nights circulation types: BM HB HM ... ridge over Central Europe high over British Isles high over Central Europe HFZ high over Scandinavia HNFA high over North Atlantic ... “efficiency” of a circulation type to produce a LLJ over Hanover for 20 months in the years 2001 to 2003 12 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research height in m and speed in m/s of LLJ over Hannover 5.2001 – 4.2003 shear = 0.02 1/s 13 29.01.2014 shear = 0.05 1/s Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations shear = 0.1 1/s Institute for Meteorology and Climate Research – Atmospheric Environmental Research annual variation of LLJ core height Hannover 5.2001 – 4.2003 14 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research LLJ wind speed compared to the driving pressure gradient force positive correlation 15 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research LLJ wind speed compared to the relative humidity negative correlation 16 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research shear above and below a height of 160 m in 1/s Hannover 5.2001 – 4.2003 17 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research directional variation of LLJ directional shear Hannover 5.2001 – 4.2003 18 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research Geostrophy ratio vs. geostrophic wind speed Hannover 5.2001 – 4.2003 speed-up until maximum shear is reached further driving leads to higher LLJ core heights keeping shear constant remaining scatter in maximum shear probably due to thermal stratification 19 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research Summary Climatology - LLJ occur in nearly 22% of all nights (in de Bilt ca. 20%) - jet cores between 135 and 650 m height (height slightly increases during the year) - jet core speed at 7 to 23 m/s (core height and core speed positively correlated) correlation to driving forces - 850 hPa wind between 1 and 18 m/s (Kottmeier et al. 1983: 6-11 m/s) - jet core speed positively correlated to 850 hPa wind (maximum at 13 m/s) - jet core speed negatively correlated to 850 hPa relative humidity dynamical implications on wind turbines - speed shear over the rotor plane between 0.04 and 0.08 1/s - directional shear over rotor plane between 0.1 and 0.2 degrees/m overall behaviour - wind speeds up until the maximum shear between 0.04 and 0.08 1/s is reached - further driving increases LLJ core height keeping shear constant 20 29.01.2014 Prof. Dr. Stefan Emeis | Low-level jets from SODAR observations Institute for Meteorology and Climate Research – Atmospheric Environmental Research Thank you very much for your attention KIT – University of the State of Baden-Württemberg and National Large-scale Research Center of the Helmholtz Association KIT – die Kooperation von IMK-IFU Atmosphärische Umweltforschung Forschungszentrum Karlsruhe GmbH und Universität Karlsruhe (TH) Garmisch-Partenkirchen www.imkifu.kit.edu
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